The present invention generally pertains to devices for treating aneurysms. More specifically, the present invention pertains to occlusion systems for the treatment of aneurysms.
Several methods of treating aneurysms have been attempted, with varying degrees of success. For example, open craniotomy is a procedure by which an aneurysm is located, and treated, extravascularly. This type of procedure has significant disadvantages. For example, the patient undergoing open craniotomy must undergo general anesthesia. Also, the patient undergoes a great deal of trauma in the area of the aneurysm by virtue of the fact that the surgeon must sever various tissues in order to reach the aneurysm. In treating cerebral aneurysms extravascularly, for instances, the surgeon must typically remove a portion of the patient's skull, and must also traumatize brain tissue in order to reach the aneurysm.
Other techniques used in treating aneurysms are performed endovascularly. Such techniques typically involve attempting to form a mass within the sac of the aneurysm. Typically, a microcatheter is used to access the aneurysm. The distal tip of the micro catheter is placed within the sac of the aneurysm, and the microcatheter is used to inject embolic material into the sac of the aneurysm. The embolic material includes, for example, detachable coils or an embolic agent, such as a liquid polymer. The injection of these types of embolic materials suffer from disadvantages, most of which are associated with migration of the embolic material out of the aneurysm into the parent artery. This can cause permanent and irreversible occlusion of the parent artery.
For example, when detachable coils are used to occlude an aneurysm which does not have a well defined neck region, the detachable coils can migrate out of the sac of the aneurysm and into the parent artery. Further, it is, at times, difficult to gauge exactly how full the sac of the aneurysm is when detachable coils are being injected. Therefore, there is a risk of overfilling the aneurysm in which case the detachable coils also spill out into the parent artery.
Another disadvantage of detachable coils involves coil compaction over time. After filling the aneurysm, there remains space between the coils. Continued hemodynamic forces from the circulation act to compact the coil mass resulting in a cavity in the aneurysm neck. Thus, the aneurysm can recanalize.
Embolic agent migration is also a problem. For instance, where a liquid polymer is injected into the sac of the aneurysm, it can migrate out of the sac of the aneurysm due to the hemodynamics of the system. This can also lead to irreversible occlusion of the parent vessel.
Techniques have been attempted in order to deal with the disadvantages associated with embolic material migration to the parent vessel. Some such techniques, commonly referred to as flow arrest techniques, typically involve temporarily occluding the parent vessel proximal of the aneurysm, so that no blood flow occurs through the parent vessel, until a thrombotic mass has formed in the sac of the aneurysm which helps reduce the tendency of the embolic material to migrate out of the aneurysm sac. However, thrombotic mass can dissolve through normal lysis of blood. Also, in certain cases, it is highly undesirable to occlude the parent vessel even temporarily. Therefore, this technique is, at times, not available as a treatment option. In addition, even occluding the parent vessel may not prevent all embolic material migration into the parent vessel.
Another endovascular technique for treating aneurysms involves inserting a detachable balloon into the sac of the aneurysm using a microcatheter. The detachable balloon is then inflated using saline and/or contrast fluid. The balloon is then detached from the microcatheter and left within the sac of the aneurysm in an attempt to fill the sac of the aneurysm. However, detachable balloons also suffer disadvantages. For example, detachable balloons, when inflated, typically will not conform to the interior configuration of the aneurysm sac. Instead, the detachable balloon requires the aneurysm sac to conform to the exterior surface of the detachable balloon. Thus, there is an increased risk that the detachable balloon will rupture the sac of the aneurysm. Further, detachable balloons can rupture and migrate out of the aneurysm.